I haven't seen a lot of responses so let me toss in my 2 cents worth.
I own two US Towers MDX-589-MDPL, a LM470D, and HyGain HD-70, plus 120'
and 100' sticks of Rohn 45.
I would not be very excited about any of your three options below, and I
must admit, my feelings are consistent with those of Mark W0NCL
immediately below. My recommendation would be to bite the bullet, sell
off the rotor you have (whatever it is that is too big to go into your
tower) and use one that will let you crank it down fully.
The reasons for this is that none of your three options are very
attractive. If you have to extend the tower to 30 feet because the rotor
will not let the tower section retract, you may well exceed the raising
fixture capabilities to get the tower vertical. The force to get the
tower off horizontal and up the first 20 - 30 degrees is substantial at
design height (~ 23 feet) that it is going to be more difficult to get
the tower started. Worse, the tower will not be fully nested with all
sections resting on their stops when you have it vertical and are
working on the antennas or rotor. One true fear that I have with
crank-ups is the possibility of losing all fingers, toes, or feet and
hands if the tower ever shifted while on it other than fully nested.
There are guys that will climb their crank ups, but I would never do
that. I have done what everyone does, and put sections of steel pipe
through each tower section to prevent massive drops if the raising cable
ever sheared, but if anything ever happened, you would lose fingers,
toes, hands or feet anyhow. I would NEVER climb a crank-up that is
extended unless in an absolute emergency. Maybe I am too cautious, but
the possibility scares the hell out of me.
Actually, I will suggest something that I just started doing. These US
Towers HDX-89-MDPL are new and I just got all the antennas up on top of
them. I have bad arthritis in both knees now that has forced me to
abandon much climbing (I have always done all my own climbing before).
So, in thinking it through, it decided to rent a 60' "man-lift". The
ones that I rented are called a Genie and they are 4 wheel drive, diesel
powered, construction equipment. They will extend to 60' with no need
for additional outriggers to prevent tipping. They are easy to learn to
control and operate. I had my towers set vertical and rented the Genie
Man-lift and was able to place the 20' .5 inch wall masts, and all yagis
all by myself from the man lift. It is definitely the way to go. It cost
me ~ $450,00 for 8 engine hours of use. I got them delivered on Friday,
and picked up on Monday. The fee included ~100.00 "delivery fee" to drop
the thing off at my QTH on a semi-tractor trailer. All in all, it hurt a
while the first time I did it, but after the first time, I have
considered it money VERY well spent. I'd do it again in a second.
Smaller versions of these same devices can be rented from consumer
rental equipment places for about $150.00 a day and will extend up to
about 30'. These smaller ones tend to be battery or 120 volt hydraulic
powered. Load issues are more critical with the smaller units than with
the piece of equipment that I rented, but guys on the reflector have
used them to good effect also.
Also, crank ups tend to have all diagnonal bracing rods and trying to
stand on them for any length of time, even fully collapsed, is a major
pain. I have gone to liking crank ups as my age increases, but I hate
many aspects of working on them. And if you run yagis of any serious
size on a crank up, the feature of being able to tilt it over to work on
the beam is a largely false feature since anything that I ever seem to
need to work on is too far off the ground to be able to get to
regardless of how I have the antenna rotated when it is tilted down.
Short boom, short element yagis may work on a tilted tower, but a yagi
like this 620/340 never gets close enough to ground to give me any
benefit. I have heard guys call the tilt down feature a "marketing
gimmick" and that is my opinion of it. Again, small tribanders probably
works OK.
I also don't understand why you are opting for the pro-sistel rotor. I
don't see a strong need for the beef that you have with the pro-sistel
given the yagi you are choosing and the tower that you are putting it
on. The yagi, while big, is not that big, and I know that a Tailtwister
would turn it just fine. The beam specs say 16.2 sq foot of antenna, 60
kg (132 pounds), and a boom of roughly 20 feet. I am turning that much
easily with a Tailtwister (Cushcraft A3WS + 30 meter dipole, chrome-moly
mast, Force - 12 620/340 (6 elements on 20, 3 elements on 40 on a 44'
boom) with one and a buddy has been turning the 620/340 for years with a
Tailtwister even through multiple hurricanes. Maybe you have severe
constant wind gusts in the NW, but if you crank the tower down during
really heavy blows, I see no reason that you can't turn the yagi that
you propose with a lot less rotor, which will let you fully collapse the
tower and you avoid the problems to start with. Also, the LMR-470, while
a very nice tower, does not have the ratings to really want to stress it
with a very big yagi fully extended in a big wind anyhow. My U.S.Towers
are substantially tougher towers than my LM-470 and in a hurricane or
very big incoming thunderstorm, its gets nested down if at all possible.
However, Good luck with it. I'd be interested in knowing what you decide
to do....
73
Gary W5FI
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of el34guy@aol.com
Sent: Friday, January 05, 2007 10:13 AM
To: ab7r@cablespeed.com; towertalk@contesting.com
Subject: Re: [TowerTalk] Crankup tower raising
I have a crankup LM470D, to be honest Id get an alfaspid rotor so you
dont have to mess with leaving the tower up at a certain spot for
eternity. That wont be good for the cables. Eventually you will want to
move the tower and with that rotor you are stuck. Its a great rotor but
I would recommend it only on a fixed tower. btw you need to send the
optibeam to my qth for proper testing before you put it up!! 73
Mark
W0NCL
-----Original Message-----
From: ab7r@cablespeed.com
To: towertalk@contesting.com
Sent: Fri, 5 Jan 2007 8:52 AM
Subject: [TowerTalk] Crankup tower raising
GM all!
Finally getting ready to raise my HG-70D tower soon. On
it will be an Optibeam OB12-6 and nothing else. The rotor
is a ProSistel.
Looking for advise on how best to do this.
With that rotor, I have to keep the tower extended to
about 30ft due to the motor sticking out the side. Should
I:
1. Install the rotor at ground level and then raise the
tower (raising fixture) and install the antenna with the
tower vertical.....or
2. Keep the tower fully retracted and install the mast
and antenna from ground level and the raise it and install
the rotor once vertical....or
3. Just raise the tower and install both the rotor and
antenna once vertical?
Tnx and hope everyone had a fine New Year.
73
Greg
AB7R
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